FRONT PAGES: Ventilation Matters — Engineering Airflow To Avoid Spreading The COVID-19

dWeb.News Article from Daniel Webster dWeb.News

— WASHINGTON — November 2, 2021 — We now know that it spreads primarily via airborne transmission as we near two years of the COVID -19 epidemic. The virus is carried inside microscopic droplets of aerosol that are released from the airways when we cough, sneeze, speak, shout, cough, or sing. The virus then floats in the air where it can be inhaled and transmitted.

This inspired researchers in India to explore how we can better understand and engineer airflow to mitigate the transmission of COVID-19. They used their expertise in airflow around engines and aircraft to adjust the airflow inside indoor spaces.

In Physics of Fluids ,, they report computer simulations of the airflow in a public washroom that show infectious aerosols can persist up to 10 longer than the rest of a room. These dead zones are often found around furniture or in corners.

Washrooms produce aerosols. They can be found in offices, schools, hospitals, planes, trains and other public places. They are a source of infection transmission in densely populated areas of India.

” We explored a single-person facility that was used by many people, one after the other,” Krishnendu Sinha of the Indian Institute of Technology Bombay, a professor of aeronautical engineering. “I have a similar bathroom in my home, which makes it easier to study.” Mobility was restricted, and laboratories were closed, but this allowed us to continue our study during the lockdown.”

The researchers discovered that chances of infection are significantly higher in a dead zone.

“Surprisingly, they can be near a door or window, or right next to where an air conditioner is blowing in air,” he said. “You might expect these to be safe zones, but they are not.”

Computer simulations show “air flows in circuitous routes, like a vortex,” said Vivek Kumar, a co-author. “Ideally, the air should be removed continuously from all rooms and replaced with fresh air. It’s difficult to do this when the air is circulating in a dead area . The biggest question about airflow is how to ventilate indoor spaces to reduce infection spread. What are the best places to place fans and ventilation conduits? How many should there be? How much air should flow through each one?

” Currently ventilation design is often based upon air changes per hour, Sinha said. Sinha stated that these calculations assume that fresh air is reaching every corner uniformly. Computer simulations and real-world experiments in a washroom have shown that this is not the case.

“ACH can also be 10 lower for dead areas. Ventilation systems that are more effective against the virus can be designed using fans and ducts that are based on air circulation in the room. Blindly increasing the volume of air through existing ducts will not solve the problem.”

The article, “Effect of recirculation zones on the ventilation of a public washroom,” is authored by Krishnendu Sinha, Mani Shankar Yadav, Utkarsh Verma, Janani Srree Murallidharan, and Vivek Kumar. It will appear in Physics of Fluids on Nov. 2, 2021 (DOI: 10.1063/5.0064337). After that date, it can be accessed at: https://aip.scitation.org/doi/10.1063/5.0064337.

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